


Year of the Wolf

by Flamefriends



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Alternate Universe - Underswap, Bestiality, Ecto-Genitalia (Undertale), FellWolves AU, Fontcest, Furry, M/M, Mating, Other, Skeleton Heat, Underfell Papyrus (Wolf), Underfell Sans (Wolf), Underswap Papyrus, Underswap Sans, edgeberry
Language: English
Status: Completed
Published: 2016-07-01
Updated: 2016-07-01
Packaged: 2018-07-19 11:23:31
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,234
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7359295
Author URL: https://archiveofourown.org/users/Flamefriends/pseuds/Flamefriends
Summary: <blockquote class="userstuff">
              <p>It's been a year since the Underswap brothers adopted the two FellWolves brothers. They've never been this friendly before, especially not the much larger wolf "Boss." What changed that made him so interested in Blueberry Sans all of a sudden? </p>
<p>Based on the FellWolves AU by Sanspar.</p>
            </blockquote>





	Year of the Wolf

It was a typical Saturday evening. The TV was playing The Napstaton Late Show, and just under the robot's voice, the occasional subtle crunch of a taco being bitten into would be heard. Along with that, though, came the just as subtle panting from the pair of recent additions to the household residents. 

It had been almost a year since Sans and Papyrus had adopted the pair of wolf brothers. The two skeletons had quickly grown to love the fur balls, with Papyrus and the smaller Cherry and Sans with the much bigger Boss. Little Cherry shared Papyrus's room, and would usually either sleep at the foot of the taller skeleton's bed, or curled up on top of his rib cage. Boss, on the other hand, liked having his own territory and had claimed the living room as his domain. Still, he seemed really attached to Sans, and would occasionally give the small skeleton affectionate nibbles.

Sans, with a soft grin, finished his second taco, then reached down to pet that same large wolf. Boss, having been curled up on the floor just in front of the couch, responded by lifting his head to look at Sans. The red-tinted eye lights that floated in the wolf's sockets glowed with affection and... something else. Something Sans couldn't quite decipher. 

"hey bro," Papyrus's voice sounded over the Late Show. "you've got a little bit of salsa on your mandible." He pointed to a spot on his own jaw for reference. 

Sans's gloved hand flew to his lower jaw, and sure enough, when he pulled that glove away, there were salsa stains on the tips. Sans's face contorted to a sheepish expression, and he looked around to find the closest napkin. However, while he was looking, Boss moved into action. He put his enormous paws on either side of Sans, bringing his face close, then started licking and nibbling Sans's mandible. 

"B-Boss!!!" Sans squealed, throwing his hands up to try and fight off the large body of bones and fluff. Sure, the grooming was nice, but it made the guardsman-to-be a little embarrassed. By the angel, his brother was sitting right next to him! His _younger_ brother! "Boss, it's alright! I can clean myself up!" 

But the large wolf didn't stop until he was satisfied with his grooming efforts. When he finally finished, he smiled in satisfaction and quickly tapped his nose against Sans's. The poor skeleton didn't know how to handle the almost kiss from Boss, and the bright blue tint to his zygomatic proved that. 

"Someone's friendly today." Papyrus noted, snickering at his older brother's reaction to the affection. Boss looked over to the tall skeleton and made a gruff woof at him, mildly annoyed.

Both wolves had been remarkably friendly as of late, but Boss's affection levels were so uncharacteristically high, it was hard not to notice. He'd even snuck into Sans's room once and fallen asleep on the small skeleton's bed. Papyrus had found Sans trapped under one of Boss's fluffy arms like a teddy bear (a "Sansy bear," according to Papyrus.) The younger brother wouldn't stop teasing Sans afterwards.

"Alright, that's enough." Sans declared, smiling and hugging Boss. The wolf seemed content with the gesture, and went so far as to nuzzle Sans. 

Papyrus made no further comment. He reached down to pick up Cherry and hold the smaller wolf against his rib cage. He stayed there, hugging Cherry for a moment, before getting up with the wolf in his arms. "Well, we'll see you in the morning. Night, Sansy bear."

Sans rolled the eye lights in his sockets, but broke the hug with Boss in order to get up and meet Papyrus at the bottom of the stairs. "Goodnight Papy!" The small skeleton chimed, giving his brother a quick hug. Papyrus spared an arm to half hug Sans back. "I'll get the dishes, don't worry."

"Thanks bro. You're the best." Papyrus gave his brother a lazy but loving grin, then patted the other's skull. He turned his attention to the wolf in his arms. "Say goodnight to Sans, Cherry." The wolf voiced a small boof.

Sans smiled at the small wolf. "Goodnight to you too, Cherry." The two then made their way upstairs and down the hall, before disappearing into Papyrus's room for the night. 

True to his word, Sans cleaned up dinner. He washed the dishes and stored the leftovers. All the while, Boss stayed close to the small skeleton. Occasionally, he'd intentionally bump into Sans or lightly nibble him to show his affection. By the time Sans finished cleaning, he had a permanent blush on his face. But why was he reacting to Boss like this? It didn't make sense. Boss was just being affectionate, and yet those nibbles and bumps felt like something more...

Sans shook the thought from his head. No, Boss was just being lovey. Nothing more. The blue-clad skeleton made his way to his room, trying to calm his blush. Boss followed him. "You... want to sleep in my room tonight, Boss?" Sans asked when he reached his door. He was feeling a little warm, but he wouldn't shut the wolf out if he wanted to stay there tonight. He would never say it to Papyrus's face, but he was a little jealous of his brother's relationship with Cherry. Boss nodded, taking initiative and stepping inside the room. Sans shut the door behind him, as he would any other night. He knew the wolf would wake him up if he wanted something, or just open the door himself. How else could he have snuck into Sans's room that one time?

Sans moved to his closet and started to change into his night wear. He didn't think anything of it at first. A wolf was a wolf, so it wasn't like he ought to be bashful or anything. The small skeleton stripped his shirt without incident, but when he moved to pull his pants down, one of his phalanges brushed against his pelvis in such a way that it made him gasp and shudder. "Wowsers... Why am I so..." He gave the bones another testing brush with his digits. He felt a shiver run the length of his spine, and it caused Sans to voice a small, held back moan. "Sensitive...?" 

Stars, he must have gone into heat. It was around that time of year, after all. Sans internally cursed himself. He hated his heat. It was just so embarrassing and-- 

Sans's train of thought was cut off when he felt Boss's face pressed against his exposed pelvis. The wolf sniffed at those sensitive bones, and even licked them. Sans tensed up, voicing a small yelp before taking a few paces away. He turned to the large wolf, his soul pulsing wildly and his entire face slight with blue blush. He held a tight grip on the pajama pants he'd been about to put on. "Boss! What was that for!?" 

Boss took a few paces towards Sans, his tail raised high and proudly. With each step that Boss took forward, Sans took two steps back. Because of their height difference though, Sans had to take that many or he would be caught by Boss. Unfortunately for Sans, there was only so much space he had to work with. It wasn't three Boss paces before Sans backed into his bed. He was trapped. "Boss...?"

The wolf finally closed the distance between himself and Sans. Using his front paws, Boss hugged the small skeleton. Then, he gently started biting the crook of Sans's neck. The small skeleton immediately reacted, a quiet but high pitched moan escaping him. Stars, his cervical vertebrae were sensitive too. Boss's teeth felt amazing against them. Sans felt his grip on his night clothes loosen. Was this it? Was he giving up that easily? Some small part of him wanted to fight. He knew what Boss wanted and he was just so embarrassed by the idea. But by the angel, Boss's teeth felt so right biting into his neck... Sans ultimately let his pajamas fall to the floor. His now-free hands moved to grip the edge of the bed for support.

Then there was a moment where time stood still. Where Boss's strong, furry arms and gentle but forceful bite sent the small guardsman-to-be into a state of bliss. It felt like heaven on earth, and the small skeleton relaxed against it. "...Ok..." It was barely above a whisper, but Sans knew Boss had heard it. The wolf pressed himself against Sans, and Sans couldn't help but pull himself closer. For a fleeting moment, Sans thought he had reached the pinnacle of pleasure. 

He thought wrong. Just a moment after they drew closer to each other, Boss started grinding his pelvis against the other's. Sans gasped, an involuntary shiver running up his spine, followed by a few high pitched (but trying to be quiet) moans. His mind started to grow hazy as Boss worked to stimulate the both of them. It just felt so good. He couldn't remember when exactly he started grinding back. 

"B-Bos-- haaa..." Sans could already feel his magic beginning to construct what he knew Boss was looking for. "I... Boss, I-- mmnh... I need it..." His voice was a higher pitched whine. The alpha wolf stopped his advances. He pulled away from his chosen mate's neck to look directly at him. "Please..." Sans begged. The lights in his sockets held a desperate plea. 

Boss's expression softened. He nuzzled his mate, then climbed up on the bed. Sans took a moment to mentally prepare himself, then crawled after the wolf, his night clothes completely forgotten. His magic had finished forming in his pelvis, and the simulation from before, as well as the anticipation for what was to come, left his glowing pussy moist to the touch, liquid magic making his entry slick. Boss had already removed his pants, and was brandishing a thick, red member of his own. The sight gave Sans chills. He wanted it. 

Just like earlier, Boss moved his head close to Sans's pelvis. The new development had him curious, and the alpha licked the solid magic to test his mate's readiness. Sans let out a shuddered moan in response to the action and clawed at the sheets of his bed. The wolf smirked, then moved to mount his mate. Sans let him, spreading his legs a bit for Boss on his hands and knees. He prepared himself for what he knew was coming next.

Boss positioned himself on top of Sans, letting the tip of his member press against Sans's opening. Then, all at once, Boss started thrusting into his mate, ramming into Sans's conjured pussy and sliding deeper and deeper inside with each thrust. Sans had to bite his pillow to muffle his scream-like moans. It felt so amazing, being pounded into oblivion. He couldn't think, only feel the sheer power that Boss was thrusting into him. Like a tsunami of pleasure crashing into him all at once. Sans rolled his hips against the other, trying to take in as much of his mate's length as he could. For a while, the only sounds that could be heard were the soft grunts from Boss and the high pitched screams of pleasure from Sans being muffled around a pillow. 

With so much mindless pleasure, it didn't take long for either of them to come. Sans felt himself close around Boss, and Boss in turn swelled inside Sans. Locked together like that, neither of them could really move together, but it didn't matter. Sans throbbed around Boss's knot, knowing they were both on the edge. When they finally did come together, Sans practically melted against the pleasure. Condensed red magic coated Sans's pelvis, spine, ribs, and soul from Boss's release, and Sans knew that his entry was probably soaked with his own magic. A testament to Boss's claim over his mate. Now that they were tied together, Sans was completely at the mercy of the alpha wolf until Boss's knot relaxed. He didn't want it to end though. It felt so right to have the large wolf inside him. He wanted to stay like this forever.

"Boss..." The small skeleton whispered. He looked up, shifting just enough so he could press his mostly flat teeth against the wolf's sharper ones. Boss didn't seem to know what to make of the kiss at first, but once Sans started lapping at his teeth, Boss seemed to understand. The alpha opened his mouth, granting Sans access to his tongue. The smaller skeleton eagerly and desperately dove into the kiss, wrapping his tongue around his mate's. Boss, catching on quickly, mirrored Sans's advances while he fell on his side. Sans snuggled up to Boss, wrapping his legs around his mate's lumbar vertebrae and his arms around the other's rib cage. The alpha, in turn, pulled Sans close with his paws into a comforting embrace. 

And they stayed like that, enveloped in a mutual embrace and cuddling each other. Even after Boss's knot relaxed and their tie was broken, Sans made no move to pull away, nor did Boss. With everything that had happened, Sans wasn't surprised when the wave of exhaustion hit. The little skeleton relaxed, letting his mate hold him close while he drifted off to sleep. In the back of Sans's mind, he hoped Papyrus hadn't heard any of that.

**Author's Note:**

> I hope you enjoyed! I actually spent a good few hours researching wolf behavior to make sure I got this right. Special thank you to Sanspar for making this AU and showing my inner furry to be let out! XD
> 
> Thank you so much Cloaked1 for drawing this amazing piece of art! You're amazing!


End file.
